dMZX Forums: c0? Overlay Inherits Background Color of Underlaying Layer -> Archived MegaZeux Bugs -> Tracker

This is definitely one of those "I didn't even know this was a bug" moments…

Issue: Overlay tiles with a blank background color ("c0?") inherit the background color of any tile underneath it.
Versions Affected: v2.51 s1 to v2.93
Introduced in Version: v2.51 s1
Operating System: DOS, Windows, more than likely others…

Further Details
Alright, so. There's a… "feature"? "Bug"? In MegaZeux v2.51 s1. Starting very specifically with that version, any overlay with a background value of 0 will inherit the background value of whatever it passes over. I honestly remember this from a long time ago (probably around the time these were first being released) and I'm pretty sure I assumed it was intentional. I might've even commented on it somewhere, but I have no idea. Regardless, it was a thing that I accepted.

While discussing bugs and issues with the modern version of MegaZeux with someone, I brought to their attention that in "classic" MegaZeux, overlays will always maintain their selected colors regardless of what they pass over. For example, if an overlay with a back background passes over a tile with a yellow background, the overlay will keep its lack of background color. In mentioning this, I genuinely surprised them as they forgot that wasn't the standard behavior for the original MegaZeux. They also mentioned it's been around since v2.51 s1. So, I did some research.

Upon looking through the change log for 2.51 s1, I noticed that it doesn't mention the new overlay behavior anywhere. In fact, s1 doesn't even have a Help File! I checked s3 as well, and… that one doesn't even mention anything earlier than s2! Finally, I checked the manual's change logs. Again, no mention of the changed overlay behavior in s1… but I did find this under s3's changes:

Quote

This tells me that JZig was aware of it, and apparently there was some kind of bug involving not inheriting the background color, but they fixed it? Weird.

Anyway, it was recommended to me that I file this as a bug report, so here I am. Researching this, I have to wonder if this change was genuinely intentional and why it was undocumented. And why just the background? Why not make c?0 symbols inherit foreground colors, too? Seems odd…

Relevant Screenshots

An overlay of c00 double-pipe characters (205 / $CD) rendering over a rainbow background in MegaZeux v2.51 and v2.51 s1
Note: The upper-leftmost tile with a blue background is the player.

This post has been edited by Joseph Collins: 21 January 2024 - 10:22 AM

Updating status to: Confirmed
Updating severity to: 2 - Fair
Updating version to: 2.93

It is an intentional feature and it was added to provide pseudo-transparency, AFAIK. It shouldn't be applied to 2.51 worlds that don't expect it, though. I wonder if any 2.51 worlds actually did expect this effect when played in newer versions, though.

I have made a critical error. Seemingly, c0? overlays capturing the background was always intended.

I just checked MegaZeux verions 2.02, 2.07, and the cobbled-together 2.50. In each and every one of these versions, overlays using black as a background inherits the background color of the tile underneath it. So… it seems like v2.51 was the odd one out, here; being able to use solid c0? normally was, in fact, an anomaly. Seemingly.

I (also) wonder if any game worlds intentionally made use of this 2.51-exclusive feature…?

This post has been edited by Joseph Collins: 22 January 2024 - 09:03 AM

Updating status to: Closed - No Change

Since this bug is isolated to 2.51 specifically, it's probably impossible to ever detect games that rely on it automatically. I don't think it will ever be possible to support this in any meaningful way. Closing this for now.

Moving to: Archived MegaZeux Bugs